1. Field of the Invention
This invention relates broadly to audio speaker systems. More particularly, this invention relates to horn-type audio speaker systems.
2. State of the Art
Loudspeaker systems typically employ one or more of the following speaker elements: i) a sub-woofer that reproduces extremely low frequencies from about 20 Hz to 100 Hz; ii) a woofer that reproduces low frequencies from about 100 Hz to 500 Hz; iii) a mid-range speaker that reproduces frequencies from about 500 Hz to 6 kHz; and iv) a tweeter that reproduces high frequencies from about 6 kHz to 11–12 kHz (and possibly to 20 kHz). In such systems, cross-over circuitry delivers the appropriate frequency range to the separate speakers. There are two ways that the cross-over circuitry can be connected to the speaker system. In low and medium power applications, the cross-over circuitry is connected after the amplifier. In such configurations, the cross-over circuitry is typically disposed within the speaker cabinet. For high power applications, the cross-over circuitry is connected before the amplifier.
Sub-woofers, woofers and mid-range speakers typically emit sound in a highly dispersed manner. In contrast, tweeters typically emit sound in a highly directional manner. Thus, the dispersion pattern of the tweeter (which is the extent to which the tweeter yields acoustic radiation over a given area) is of particular importance in designing a speaker which has wider dispersion overall. There are several different types of tweeters including cone tweeters, dome tweeters, and horn tweeters.
Cone tweeters utilize a shallow cone surface with a sound producing diagram at its apex. Cone tweeters are efficient and most economical, and typically provide a narrow dispersion pattern.
Dome tweeters utilize a dome diaphragm to produce sound. The dome diaphragm is typically made of light hard metal (such as titanium), rigid plastic compounds, or soft silk-like material. Dome tweeters are efficient, yet typically provide narrow dispersion patterns for frequency components above 10 kHz.
Horn tweeters utilize a horn surface (which is typically curvilinear or exponential in nature) with a relatively small sound-producing element at its apex. Typically, horn tweeters are designed to provide a narrow dispersion pattern with a dispersion angle between 60 and 90 degrees for the high frequency audio signal components supplied thereto by the crossover-circuitry.
A wide dispersion pattern is desirable in some acoustic applications, such as distributed audio installations that require many loudspeakers for the desired acoustic coverage of the listening space. In such applications, the wide dispersion pattern reduces the number of speakers required to cover the listening area, and thus reduces costs. As described above, conventional tweeter designs are limited in their dispersion pattern (generally less than 90 degrees) for high frequency audio signal components, and thus are unsuitable for use in these applications. Thus, there remains a need in the art to provide audio speaker components that have wide angle dispersion characteristics for high frequency signal components and thus are suitable for use in acoustic applications requiring wide coverage such as distributed audio installations.
Moreover, it is desirous in many of these applications that the speaker components reproduce frequencies generally supported by a mid-range speaker (typically below 6 kHz down to 500 Hz). This extended frequency range also reduces the number of speakers required to cover the listening area and reduces costs. As described above, conventional tweeter designs support only high frequency components and thus fail to provide the benefits of an extended frequency range. Therefore, there remains a need in the art to provide audio speaker components that have wide angle dispersion characteristics over an extended frequency range.
Finally, it is desirous in many of these applications that the speaker provide a uniform dispersion pattern (typically referred to as “constant beamwidth” or “constant directivity”) with respect to the area covered by the speaker. This feature simplifies the layout and design of the loudspeakers of the system in order to provide uniform coverage over the intended listening area. However, typical “constant beamwidth” horn tweeters are limited in their dispersion pattern (generally less than 90 degrees), and thus are disadvantageous in these applications. Therefore, there remains a need in the art to provide audio speaker elements that have uniform dispersion characteristics suitable for such wide coverage acoustic applications.